Wrote this one because I didn't find this one: Progress. In some ways mine is simpler and prettier (although less readable). In case someone finds it useful - here it is, up for the taking (or improving)...
proc progres {cur tot} {
if {$cur % ($tot/300)} { return }
set total 76
set half [expr {$total/2}]
set percent [expr {100.*$cur/$tot}]
set val (\ [format "%6.2f%%" $percent]\ )
set str "\r|[string repeat = [expr {round($percent*$total/100)}]][string repeat { } [expr {$total-round($percent*$total/100)}]]|"
set str "[string range $str 0 $half]$val[string range $str [expr {$half+[string length $val]-1}] end]"
puts -nonewline stderr $str
}